While the Portland Streetcar grinds toward South Waterfront, the line's potential further extension is generating "not in my backyard'' shouts from well-heeled residents along the Willamette River.

The NIMBYism alert ahead from wealthy homeowners comes as Metro enters the early stages of an 18-month study of transportation options between Portland and Lake Oswego.

Traffic projections on already-congested Highway 43 estimate an increase of up to 25 percent over the next two decades on the narrow, four-lane highway. One solution: a roughly seven-mile extension of the streetcar into downtown Lake Oswego, rumbling past palatial homes with values as high as $3 million in Riverwood, Dunthorpe and Briarwood.

Richard Brandman, Metro's transportation planning director, calls the idea "at the embryonic stage" and promises extensive public involvement. If the streetcar proposal survives Metro's study, construction on the rail option lies at least four years away, Brandman says.

But Charles Ormsby, a neighborhood activist in Briarwood, is worried now about extending the streetcar along the Willamette Shore Rail Line past cliffs and through a limited-access tunnel.

"There's three concerns: Solitude. Security. Safety," Ormsby says. "These are quiet neighborhoods. Plus, the drivers sit behind locked doors. What if something happens as these trains pass over the steep hills around Riverdale?"

Among his concerns: cop response time to muggers, crazies, terrorism, accidents, and potential earthquakes.

Briarwood homeowner William Gilmer says the streetcar "would do absolutely nothing for our neighborhood," both reducing property values and killing his plans to build a second house nearby.

In Riverwood, the line comes within 6 feet of several backyards, porches, living-room windows and one tennis court. Further down the line in Briarwood, it sits within a few dozen feet of houses.

An antique excursion trolley uses the line primarily from May through October, completing 20 two-hour round trips a week between Lake Oswego and Portland. The Portland Streetcar, which hits downtown stops every 13 minutes on weekdays, would pass by much more often every day of the year.

The streetcar extension isn't Metro's only option. Other ideas under consideration include a river transit service and a rapid bus line that could require pullouts or its own lane on Highway 43.

Dave Wiley, an area resident for over 50 years, isn't worried about the noise of increased rail traffic and recalls an era when freight trains once used the tracks. "One of them passed through here every morning at 5 am," Wiley says. "We learned to sleep through it."